According to the Mayo Clinic, falls and car accidents are the most common causes of traumatic brain injuries. Head trauma is not the only way to damage structures within the brain; a sudden jolt could send the brain crashing into the skull, and the impact of an explosion causes pressure waves that may affect brain function. 

After any blow to the head, it is a good idea to see a doctor. A physical exam and scans of the brain may reveal symptoms such as slow responses, dilated pupils, torn blood vessels or other signs of TBI. The health care provider may recommend a follow-up appointment to watch for hidden symptoms or complications. 

Hidden symptoms 

People with brain injuries may focus on symptoms such as headache, ringing in the ears and blurred vision, and when these subside, they may feel that they have recovered. They may still develop other issues, or begin to notice them later. For example, at work or school in the days that follow the TBI, someone may have unusual trouble focusing or processing information. Mood swings, irritability, changes in sleep patterns and sensory changes may also become an issue as the days and weeks go by. 

Complications 

Initial scans may not reveal small tears in blood vessels, and blood may seep and pool slowly. Pressure may build up inside the skull if this occurs, causing damage to other areas of the brain. Fluid build-up could also lead to seizures, infections, blood vessel damage, severe headaches and vertigo. 

According to the American Association of Neurological Surgeons, some issues, such as an otherwise normal drop in blood pressure or increases in blood sugars or body temperature, may cause further neurological damage.